A loosely coupled capacitive power transfer system with LC compensation circuit topology

This paper proposes a double-sided LC compensated capacitive power transfer (CPT) system, which is the dual of the conventional series-series (SS) compensated inductive power transfer (IPT) system. Four metal plates are arranged as the capacitive coupler, and there are coupling capacitances between each pair of plates. At each side, a compensation capacitor is connected in parallel with the plates, and its value is usually much larger than the coupling capacitance between the plates, which results in a loosely coupled CPT system. In this paper, the fundamental harmonics approximation (FHA) method is used to analyze the circuit working principle. It shows that the system can work at constant current mode. An expression for the system output power is expressed, which is similar to that of the SS compensated IPT system. A 150W input power CPT system is therefore designed as an example to validate the compensation topology. The experimental results show that the dc to dc efficiency of the system is 66.67% when the air-gap distance is 180 mm and the switching frequency is 1.5 MHz.